Indoor structure that simulates an outdoor environment is used, for example, in dioramas, theaters, and planetaria. Such structures used in dioramas and theaters typically involve ceilings painted either blue to simulate daylight sky or black with painted stars to simulate night sky. Such structures used in planetaria typically include extremely elaborate optical equipment used to project star patterns on a concave surface from a projector located in the same room as the concave surface for the benefit of an audience located in the same room as the concave surface. The former types of structures, however, are not very realistic, and the latter type of structure is extremely expensive.